The invention relates to a device for feeding objects which have a shape of essentially flat but flexible sheets or blanks of sheet material, piece by piece from the top of a magazine consisting of a plurality of such objects which are arranged on top of one another, comprising separation means for parting the uppermost object from underlying objects in the magazine, before it is moved from the magazine, and first motion devices for removing the parted uppermost object from the magazine.
Devices of the above mentioned kind have many industrial applications. One such application is packaging machines, in which sheets or blanks shall be fed from a stack into a machine, where the sheet or blank is folded to form a package and is also possibly filled automatically. In order that such a machine shall operate without interruptions all sub-operations must function from the feeding in of said sheets or blanks to the feeding out of the finished package. An operation which has always been a problem is the feeding of the sheets or blanks from a storage containing the sheets or blanks, because the objects often have a tendency to stick together. The adherence may depend on electrostatic charges but is particularly pronounced in the case of packaging blanks that have punched out holes, flaps, slots, etc., which easily cause the blanks to hitch onto one another. In order to avoid this, devices of the above mentioned kind have been developed, which comprise separation means for parting the uppermost object from the underlying objects in the magazine before the object is moved from the magazine. Such a separation means may comprise rotating, spiked rollers, which work against a pair of opposite edges of the sheet/blank. The rollers may be combined with air nozzles, which blow in air between the sheets to part them. The devices which are commercially available at the present, however, do not solve the problem satisfactorily, at least not when the objects in question have the shape of paperboard blanks having punched out flaps, holes, slots, etc., which make the separation difficult.
It is also crucial that the devices which are employed for feeding sheets or blanks into a packaging machine piece by piece can operate completely continuously. If, for example, the feeding in device needs to be stopped for replenishing the magazine with packaging blanks, the whole process of the integrated packaging machine is interrupted. This is also a problem that has not been solved satisfactorily according to prior art.
An aim of the invention is to solve the above mentioned problems. The first of these, namely to provide a device that has well functioning separation means for parting the uppermost object from the underlying objects in a magazine, according to the invention, is solved therein that said separation means comprises members provided to bend the uppermost object to adopt an upwardly convex shape, while the adjacently underlying object is bent to a less convex shape than the uppermost object, or it remains at least essentially flat, before the uppermost object has been removed from the magazine.
The second problem, namely to provide a device mentioned in the preamble, which can operate continuously is solved according to the invention therein that said magazine, in which the uppermost object is parted from the underlying objects of the magazine before it is moved from the magazine, is a buffer store; that the device also contains a storage comprising a stack which may consist of an essentially larger number of objects than the buffer store; and that second motion means are provided to replenish the buffer store from the storage. Preferably said storage is provided under the buffer store, wherein said second motion means are provided to move said stack upwards in the storage in order to replenish the buffer store as the buffer store is successively emptied by feeding out objects from the buffer store piece by piece, and wherein locking means are provided to keep the buffer store in place in feeding out position, while the storage is being replenished by a new stack of objects.
Further characteristic features and aspects as well as advantages of the invention will be apparent from the appending patent claims and from the following description of a preferred embodiment.
It shall in this connection also be mentioned that said sheets or blanks may consist of widely different materials, such as for example paper, paperboard, plastic, metal foil, etc. as well as of combinations of two or more of said materials. The terms sheets or blanks of sheet material therefore are not restricted to any specific types of materials.